The embodiments described herein relate generally to electrical energy meters, and in particular to a meter having a tamper-resistant or tamper-evident cover.
Electrical energy meters, also referred to as “watt-hour meters,” are used on a widespread basis in residential, commercial, and industrial applications to measure the amounts of utility, such as electricity, gas, and the like, that are being utilized by customers. Meters are typically mounted on an exterior or interior wall of a building being monitored, and generally include a base and a cover attached to the base. The base supports a rate metering device attached to a power box, and a utility usage display. The cover can be substantially clear or include a clear portion that allows the usage display to be viewed through the cover.
Referring to FIGS. 1 and 2, a conventionally constructed meter 20 is schematically illustrated as including a base 22 having a mounting location 24 that supports the rate metering device (not shown), and a cover 26 attached to the base 22. The base 22 includes an outer lip 31 that defines the perimeter of the cover 26, and is sized to fit over the perimeter of the base 22. The base 22 further includes a plurality of circumferentially spaced retention lugs 30 that extend radially in from the lip 31. Each retention lug 30 can define a retention pocket 32 configured to receive a complementary plurality of locking members 33 that are circumferentially spaced about the perimeter of the base 22. A stop plate 34 is disposed at one end of the locking member 33 on the base 22. The meter 20 can thus be assembled by fitting the cover 26 over the base 22 such that the retention pockets 32 are aligned with the locking members 33.
The cover 26 can then be rotated in a direction (Arrow A as illustrated) that causes the retention pockets 32 to receive the complementary locking members 33. Engagement between the stop plates 34 and the retention lugs 30 prevent over-rotation of the cover 26. The locking members 33 can have a thickness that causes a pressure-fit with the retention lugs 30 inside the pockets 32 that resists but does not prevent counter-rotation (in the direction of Arrow B) that detaches the cover 26 from the base 22.
It has been a goal of conventional energy meter design to provide tamper resistant meters. Meter covers were historically made from glass to provide transparency that enabled viewing of usage display. Unfortunately, the glass covers were subject to breakage by vandals. The development of impact resistant plastic such as polycarbonate allowed for plastic covers to replace the conventional glass covers to greatly reduce vandalism. Covers can further be provided with a seal that is installed between the meter base and the cover to substantially prevent relative rotation, thereby substantially preventing tampering due to rotational detachment of the cover from the base. Unfortunately, conventional electrical meters were subject to tampering by prying the meter cover off of the base. Because the conventional meter cover could subsequently be fitted over the base into its original configuration, the indications (if any) would be sparse that the meter had been tampered with.
It is therefore desired to provide an electrical meter that has a reduced exposure to tampering, or is tamper evident.